Final answer:
Muscle spindles send information about muscle stretch to the CNS, are innervated by gamma motor neurons, and are tonically active.
Step-by-step explanation:
Muscle spindles play a crucial role in the body's ability to sense muscle stretch and maintain muscle length. Here are the key points about muscle spindles:
1. Muscle spindles are stretch receptors that send information about muscle stretch to the central nervous system (CNS). When a muscle stretches, the muscle spindles detect the change in muscle length and relay this information to the CNS.
2. Muscle spindles contain sensory neurons called intrafusal fibers. These fibers are specialized to detect muscle stretch and transmit signals to the CNS.
3. Muscle spindles are innervated by gamma motor neurons. These motor neurons regulate the sensitivity of the muscle spindles. When gamma motor neurons are activated, they cause the muscle spindles to contract and become more responsive to stretch.
4. Muscle spindles are tonically active, meaning they are constantly sending signals to the CNS even when the muscle is at rest. This baseline activity helps the CNS to continuously monitor muscle length and make adjustments to maintain muscle tone and control movement.